int led [5] = {12, 10, 8, 4};

void setup() {
  // put your setup code here, to run once:
  for(int i = 0; i <= 3; i++){
    pinMode(led[i], OUTPUT);
    digitalWrite(led[i], HIGH);
  }

}

void loop() {
  // put your main code here, to run repeatedly:
    for(int i = 0; i <= 3; i++){
    digitalWrite(led[i], LOW);
    delay(250);
    digitalWrite(led[i], HIGH);
    delay(250);
  }

}